Selective deposition of Si and Si-containing films has found many applications in semiconductor manufacturing. Recent applications include use as metal oxide semiconductor field effect transistor (MOSFET) channel stressors to enhance device mobility. Silicon germanium (SiGe) films are strong candidates for p-FET devices and carbon-doped silicon (SiC) films have been proposed for n-FET devices. Integrating embedded SiC (eSiC) films into state-of-the-art n-FET devices has been found to be extremely challenging and serious technology issues remain for SiC deposition processes, including how to deposit SiC films with reasonable cost of operating (CoO).
To achieve enhanced electron mobility in the channel of MOSFETs, it is desirable for the carbon-doped Si films to contain substitutional carbon atoms to induce tensile strain in the channel. Higher channel tensile strain can be achieved with increased substitutional carbon content in the carbon-doped Si source and drain. However, most of carbon atoms incorporated through selective SiC epitaxy process (for example at process temperature greater than 700° C.) occupy non-substitutional (i.e., interstitial) sites in the Si lattice. By lowering the growth temperature, a higher fraction of substitutional carbon level can be achieved (e.g., nearly 100% at growth temperature of 700° C.). However, the slow growth rate at these lower temperatures can be problematic for device applications, and selective deposition may not be possible at the lower temperatures. Blanket coverage of the substrate conventionally requires additional lithography and etching steps to remove the film from the unwanted areas of the substrate to form the desired pattern. These additional steps reduce throughput and increase the expense of forming patterned Si and Si-containing films.
Another approach to selectively form Si and Si-containing films involves non-selective film deposition and subsequent selective etching where areas with non-epitaxial films are substantially selectively removed due to higher etch rates than areas with epitaxial films. However, the epitaxial films are partially etched and may thus be damaged or degraded during the etching process.